Thermal electric fuse



Mai' 8, 1934. F, C, A MAR 1,958,367

jTHERMAL ELECTRIC FUSE Filed March 29. 193?.

25 "inv/l' INVENTOR- Patented .May 8, 1934 l UNITED STATES THERMAL ELECTRIC FUSE vFrank c. La Mar, New York, N. Y., mignon toI Great Western Fuse Company, New York, N. Y., a corporation of Delaware Application March 29, 1932, serial No. 601,732

6 Claims.

larly to protective devices therefor, and more especially to thermal or fusible protectivev devices.

A principal object of this invention is the production of a cartridge type electric fuse of such construction that the fusible element thereof may be renewed without the use of tools, :and-at the same time is such that the insertion of -an improper fusible element is prevented.

Other objects and advantages will appear as the descriptionof the particular physical embodiment selected to illustrate the invention progf resses and the novel features will be particularly pointed out in the appended claims. l5 In describing the invention in detail andthe particular physical embodiment selected to i1- lustrate the invention, reference will be had to the accompanying drawing vand the several views `thereon, in which like parts are designated by the same characters throughout the several views,

' and in which:

Figure 1 is a cross-sectional view of a cartridge type fuse embodying applicants invention; Fig. 2 is a cross-sectional view of the same device as shown by Fig. 1, but taken on a plane at a right angle to the plane upon which Fig. 1 is taken; Fig. 3 is a cross-sectional view of the device as shown by Fig. 1 on a plane indicated by the line III- D1 of Fig. 1 viewed in the direction of the arrows at the ends of the line; Fig. 4 is a view cor-,- responding to Fig. 3, but showing the parts in a. slightly different relation, to illustrate the adaptability ofthe device to fusible elements of different thickness; Fig. 5 is a detailed view of an operating lever used in applicants invention; Fig. 6 is a view of a portion of a device as shown by Fig. 1 illustrating a position of the operating levers preparatory to renewing the fusible element.

Numeral 1 designates the Qrdinaryand well known insulating tubular shell as ordinarily used in cartridge type electric fuses. This shell may be of any desired and appropriatematerlal such as horn fibre. Each end of the shell 1 carries a ferrule 2. In the form shown the ferrule embraces the outer periphery of the shell 1 and is suitably attached thereto so as not to rotate independently thereof by means of the tight lit, andthe supplementary rivet 3.

The ferrule 2 has its outer end 4 threaded for the reception of an apertured threaded thimble 6. The aperture 7 of the thimble is such that a shoulder 8 is formed.v

A metallic knife blade 9 is positioned in the aperture of the thimble 6. This knife blade has a shoulder 10 rigidly attached thereto.

(Cl. 20o-119)l This invention relates'to conductors, particuw A washer 11 is provided which is formed with a slot 12 to just t over and `around the knife blade. The washer. 11 is positioned against the shoulder 10 and one surface bears against the end 13 of the ferrule, while the opposite surface bears 60 against the flange 8 of the thimble. This construction prevents the knife blade 9 from moving outwardly.

In order to prevent the knife blade from moving inwardly, an insulating bar 14 is rigidly at- 65 tacled to both the knife blade 9 and the opposite knife blade 15 so that neither knife blade can move inwardly, and as the ends of the fuse are built symmetrically and identically neither knife blade, nor oppositely disposed contacting conducting member, can move outwardly.

lhe thermal or fusible element is in the form, as shown by Fig. 6, designated 16., It has slots 17 and 18 which fit around the stem of bolts 19 and 20 and is held in place by pressure exerted by the 75 heads 21 and 22 of the bolts 19 and 20 respective- "ly, being bound between then heads and the knife blades.

All of the constructions hereinbefore described are old and well known. Hretofore, however, the `heads 21l and 22 have been provided with a screw driver slot so that the insertion or removal of a thermal element such as 16 required the use of a screw driver or similar tool. Applicants invention is designed to obviate theuse either of a screw driver or any other tool in the operation of removing or replacing a thermal element.

Applicant provides bolts, such as 19 and 20 which are provided with an enlarged head, as 21, and with a screw thread as 23. The knife blades,

as 9, are also provided with an internal screw thread cooperating with a screw thread 23 of the bolt, as 19. The turning of the bolt 19 causes the head 21 to approach toward or recede from 95 the knife blade 9 thus binding the thermal element to the knife blade or providing a space in which the thermal element may be inserted preparatory to binding.

. In order to turn the bolt 19, applicant provides a plural faced, toothed or mating member, such as a small pinion 24, on each bolt. This pinion is attached rigidly to the bolt 19, preferably by passing a pin such as 25 through the pinion and the bolt 19.

In order to turn the bolt 19 an operating handie 26 is provided, shown in detail in Fig. 5. This operating handle is provided with a mating aperture or internal toothed `pinion 27 of such size that it meshes with the pinion 24. When 110 this operating handle is in place upon the pinion 24, and is drawn either to the right or left, as viewed in Fig. 1, the bolt head 21 will be `either drawn toward or caused to recede from the surface of th'e knife blade 9, and so a thermal element maybe bound or released forv renewal.

' In order to hold the operating handle k26 properly in place in mesh with the pinion v24 applicant provides a member to prevent the operating handle 26 from moving outwardly off the pin- 1 ion. This preferably takes the form of a screw thread`28 upon the bolt 19 and a nut 29 engaging the screw thread.

Although applicant has illustrated a bolt as the binding means, it is to be understoodvthat this is merely illustrative but is not intended to exclude other well known and suitable constructions wherebya head orbinding member is caused to approach or recede from a binding face.

With applicants type of fuse, if it is necessary to replace a fusible element, such as 16, the operating handles 26 are moved from the position as shown in Fig. 1 to the position as shown in Fig. 6. This .movement causes the heads 21 and `22 to separate from the face of the knife blades 9 and 15 so that the old fusible element may be removed and a new fusible element put in position. After Athe new fusible element has been put into position the operating handles 26 are returned to the position as shown in Fig. 1 thereby binding the thermal element rmly between the heads as 21 and 22 and the faces of the knife blades 9 and 15.

A custom Aamongst the makers of cartridge fuses allow certain differences lin the capacity `the greatest distance possible for'the device to exhibit between the under side of the head 2l and' the face of the knife blade 19 is obtained. 'Ihis allows the higher capacity fusible element to be inserted. Of course, anything thinner may be inserted. It is to be observed that the higher capacity is limited. This is in accordance with desire, because although no harm could come from inserting a lower capacity fusible element, much harm could come from inserting an'element of a capacity greater than the particular size cartridge is capable of carrying. For this reason applicants construction is such that a. fuse above a given limit cannot 'be inserted.

It will be readily understood that to secure different openings between the inside of thev head 21 and the face of the knife blade 9 different angular movements of the operating handles 26 are required, and that a very thick fusible element under a head, such as 21, might result in the operating handle 26 being in a posi'- tion at an angle to the position as shown in Fig. 1 when the head 21 is tightly pressed against the fusible element and the fusible element is tightlyI pressed against the face of the knife blade 9. Applicants construction provides for this contingency and is 'particularly designedto provide therefor. In order to have the operating handles in the position as shown in 1 when the fusible element is in place and the boltheads are tightened there against, the nut 29 is removedfrom the bolt 19, the operating handle 26 removed from engagement with the pinion 24 and then turned about the axis of the bolt to such an extent that it will lie in the desired angular position, and then returned into vengagement with the pinion, and the nut 29 replaced to hold the operatinghandle in position. This removal and replacement'of the operating handle ,26 may be necessary in order to provide the widest possible space between the head 21 and the face of the knifevblade 9 and then another removal and replacement may be vnecessary in order to suitably adjust the operating handle so that it will' lie in the position as shown in Fig. 1 when the thermal element .has been tightly bound.

Fig. 3 illustrates by the space 30,J the fact that a thick fusible element 1-6 is in place under the head 21 while in Fig. 4 the space 31 indicates that of operation thereof, nevertheless, I desire to -have it understood that the form selected is merely illustrative but does not exhaust the possible physical embodiments of the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a fuse of the type in which there are oppositely disposed contact conducting lmembers and a fusible element extends, from one to the other, the combination of a threaded bolt formed with an enlarged head in screw threaded engagement with a knife blade, a plural toothed member fixed upon the bolt, an operating handle engageable in different positions with said plural toothed member for rotating said plural toothed member, f

means for retaining the plural toothed member in an engaged position an abutment for engagement with the plural toothed member for limiting the longitudinal movement of the bolt whereby the bolt may be rotated by an operation of the handle so as to space the head thereof a predetermined distance from the contact conducting member, and means to connect the other end of the fusible element to the other contacting member. 1 h Y 2. In an electrical fuse of the typein which oppositely disposed contacting conducting members connected by a fusible str ip are used, the combination of a headed bolt for binding the fusible member between a contacting conducting member and the underside of the head in screw threaded engagement with a contacting conducting member, means for limiting the 1ongitudinal displacementl of the bolt, said means including an operating handle, and means for adjusting said operating handle to different angular positions upon vsaid bolt and means for retaining the operating handle .in an adjusted angular po- 3. As a binding means for holding av fusible strip to a knife Ablade terminal, the combination of a threaded bolt formed with an enlarged head in screw threadedl engagement with the knife blade,

ment for limiting the longitudinal displacement of the bolt, whereby a manipulation of the operating handle produces a space between the head of the bolt and the knife blade of no greater than a predetermined amount and whereby the operating handle may be so positioned upon the plural face member that when the fusible men.- beris bound tightly to the knife blade the operating handle will lie substantially in a desired position.

4. In a fuse, a knife blade formed with a screw threaded aperture, a screw threaded bolt engaging the screw threaded aperture, said bolt formed with an enlarged head, whereby a fusible element may be bound between the head and the knife blade, a plural face member xedly attached to the bolt, an abutment limiting the longitudinal displacement of the bolt, an operating handle formed with an aperture corresponding in size and shape with the plural face member on the bolt, whereby the operating handle may be placed I in different positions angularly about the axis of the bolt so that various degrees of longitudinal movement' of the bolt may be secured even if adjacent parts obstruct the rotation of the handle and whereby when the head of the bolt is pressed firmly against the fusible element and the fusible element is pressed rmly against the knife blade the operating handle may lie in a desired position angularly about the axis of the bolt and means for retaining the operating handle in cooperative relation with the plural face member.

5. In a fuse of the type in which a fusible element is bound to a knife blade4 by being placed between the head of a bolt screw threaded into the knife blade and the knife blade, the combination of a member xedly attached to the bolt and an operating handle formed to mate with said member on the bolt in a plurality of positions angularly about the axis of the bolt, means for retaining the operating handle in angularly adjusted position and means to limit the longitudinal movement of the bolt.

6. In a fuse of the type in which a fusible element is bound to a knife blade by being placed between the head of a bolt and the knife blade, the combination of a member formed with a screw threaded aperture for cooperation with the thread of the bolt, means for limiting longitudinal movement of the bolt, a, plural face member on the bolt, a mating operating handle adapted to be placed on the plural face member in a plurality of positions angularly about the axis of the bolt and means for retaining the operating handle in adjusted position on the plural face member.

FRANK C. LA MAR. 

